【笔记】过滤器filter

package com.cyf.web.filter;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebFilter("/*")
public class LoginFilter implements Filter {
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
//        强转
        HttpServletRequest request = (HttpServletRequest) req;
//        创建集合，放入所有要放行的路径
        String[] urls = {"/CheckServlet","/AdduserServlet","/LoginServlet","/css/","/imgs/","/login.jsp","/register.jsp","/SelectByUsernameServlet"};
//          获取访问路径
        String url = request.getRequestURL().toString();
//          遍历集合
        for (String u : urls) {
//            判断获取的路径和访问路径是否相等
            if (url.contains(u)){
//                放行
                chain.doFilter(req, resp);
                return;
            }

        }
//        获取session对象
        HttpSession session = request.getSession();
//        查看session是否有存入值
        Object emp = session.getAttribute("Emp");
        if (emp==null){
//            如果没有值，说明用户未登录
            request.setAttribute("msg","请登录");
//            跳转到登录界面
            request.getRequestDispatcher("/login.jsp").forward(request,resp);
        }else {
//            登录了就放行
            chain.doFilter(req, resp);
        }

    }
    public void destroy() {
    }

    public void init(FilterConfig config) throws ServletException {

    }

}